The president's son-in-law and senior adviser Jared Kushner has been stripped of his temporary, high-level security clearance under new rules imposed by White House Chief of Staff John Kelly designed to crack down on West Wing staff with long-pending background investigations, sources tell ABC News.

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That means Kushner, whose portfolio includes the solving the Middle East peace process, will no longer have regular access to the nation's most closely guarded secrets as the FBI continues its nearly 15-month review of his application for permanent clearance. Kelly's action was not limited to Kushner alone, the sources said.

The move became effective last Friday.

The White House would not comment on the record about Kushner’s clearance.

Kushner, who was on Capitol Hill earlier in the day, declined to answer reporters' repeated questions about his security clearance.

A spokesperson for Kushner said the move will not affect Kushner's ability to carry out tasks assigned by the president.

"As to his security clearance, Mr. Kushner has done more than what is expected of him in this process. Those involved in the process again have confirmed that there are dozens of people at Mr. Kushner's level whose process is delayed, that it is not uncommon for these clearance reviews to take this long in a new administration, and that the current backlogs are now being addressed," the spokesperson said. "No concerns were raised about Mr. Kushner's application. As General Kelly himself said, the new clearance policy will not affect Mr. Kushner's ability to continue to do the very important work he has been assigned by the President."

Sources familiar with the matter say Kushner's downgraded clearance may still allow him access to sensitive information, but details are unclear. Officials familiar with the matter stressed that Kushner, like others previously on a temporary clearance including Ivanka Trump and White House Counsel Don McGahn, could eventually receive full clearance once the background checks are complete.

Earlier this month, Kelly and McGahn implored Deputy Attorney General Rod Rosenstein to expedite Kushner's review, but Rosenstein informed the White House that the FBI could not move any faster and that the check was still ongoing, one source told ABC News.

Kelly's move came a week after he declared in a five-page memo to staff that he'd end all temporary Top Secret and Sensitive Compartmented Information clearances for staffers who have had background check investigations pending since June 2017. Kushner's application has been pending since January 2017. Sensitive compartmented information reveals sources and methods by which intelligence is gathered, making it highly valuable.

In a statement after his memo was released, Kelly said he had “full confidence” in Kushner’s abilities to advise the president, but made clear his duties were limited to “his foreign policy portfolio including overseeing our Israel-Palestinian peace effort and serving as an integral part of our relationship with Mexico.”

The directive came as Kelly faced mounting criticism for his handling of the resignation of former White House Staff Secretary Rob Porter. It was revealed earlier this month that Porter's application for top clearance had been denied by the FBI after they uncovered allegations of violent domestic abuse in his past.

One White House official questioned the wisdom of Kelly's decision, suggesting it would be unwise for the Chief of Staff "to go to war with Jared over this."

Trump said Friday that the decision on Kushner’s status was up to Kelly alone.

"General Kelly respects Jared a lot, and General Kelly will make that call,” Trump told reporters at an afternoon press conference. “I will let General Kelly make that decision. And he's going to do what's right for the country, and I have no doubt he will make the right decision."

Kushner has, at times, clashed with Kelly since he took over as chief of staff last summer and sought to impose a more stringent chain of command in the West Wing, with Kushner reporting to him, sources familiar with their relationship have told ABC. Prior to Kelly's arrival, Kushner had unlimited direct access to the President.

White House officials and sources close to Kushner would not explain how Kushner could maintain access to some highly classified information without the temporary clearance, but the office of the presidency comes with unfettered authority to declassify information, giving Trump a unique ability to share information with Kushner as he sees fit. It’s unclear if the president would exercise that authority.

National security attorney Mark Zaid, who often handles clearance cases, said in an interview with ABC that although there is nothing stopping the president from declassifying information for Kushner, the president would have to consider that "once it's declassified for one, it's declassified for all."

Zaid also says it possible the president could declassify information and then reclassify it before making it public, but by law that process would need to be documented. "The optics of that would obviously be horrible," Zaid said.

Kushner’s security clearance application has been caught up for well over a year after he failed to disclose some contacts he had with foreign officials -- including Russians -- as required by law.

Another attorney for Kushner, Jamie Gorelick, has previously stated that Kushner's security clearance form, known as an SF-86, was "prematurely submitted" and that "among other errors, [it] did not list any contacts with foreign government officials." Kushner has since updated the questionnaire multiple times to with all relevant meetings, including "over 100 calls or meetings with representatives of more than 20 countries," Gorelick told ABC News.

As a former businessman, Kushner also has numerous financial dealings that the FBI is currently reviewing, which could further account for the delay.

Nevertheless, it is very uncommon for one of the closest aides to the president to remain without formal permanent clearance more than a year into the administration. National security lawyer Bradley Moss told ABC that security clearance background checks for staffers close to the president are expedited because of the sensitivity of their position. For a senior staffer like Kushner to have a 15 month investigation, even considering his complex financial background, is "highly unusual," Moss said.

Last week President Trump seemed to blame the system, rather than Kushner himself. “We inherited a system that's broken. It's taken months and months and months to get many people that do not have the complex financial -- complicated financials, they don't have that. It's still taken months. It's a broken system,” he said.